Add (nearly) full printf support by delegating to vsprintf

hiredis.c

@@ -32,6 +32,7 @@
 #include <unistd.h>
 #include <assert.h>
 #include <errno.h>
+#include <ctype.h>
 
 #include "hiredis.h"
 #include "net.h"
@@ -639,6 +640,59 @@ int redisvFormatCommand(char **target, const char *format, va_list ap) {
             case '%':
                 current = sdscat(current,"%");
                 break;
+            default:
+                /* Try to detect printf format */
+                {
+                    char _format[16];
+                    const char *_p = c+1;
+                    size_t _l = 0;
+                    va_list _cpy;
+
+                    /* Flags */
+                    if (*_p != '\0' && *_p == '#') _p++;
+                    if (*_p != '\0' && *_p == '0') _p++;
+                    if (*_p != '\0' && *_p == '-') _p++;
+                    if (*_p != '\0' && *_p == ' ') _p++;
+                    if (*_p != '\0' && *_p == '+') _p++;
+
+                    /* Field width */
+                    while (*_p != '\0' && isdigit(*_p)) _p++;
+
+                    /* Precision */
+                    if (*_p == '.') {
+                        _p++;
+                        while (*_p != '\0' && isdigit(*_p)) _p++;
+                    }
+
+                    /* Modifiers */
+                    if (*_p != '\0') {
+                        if (*_p == 'h' || *_p == 'l') {
+                            /* Allow a single repetition for these modifiers */
+                            if (_p[0] == _p[1]) _p++;
+                            _p++;
+                        }
+                    }
+
+                    /* Conversion specifier */
+                    if (*_p != '\0' && strchr("diouxXeEfFgGaA",*_p) != NULL) {
+                        _l = (_p+1)-c;
+                        if (_l < sizeof(_format)-2) {
+                            memcpy(_format,c,_l);
+                            _format[_l] = '\0';
+                            va_copy(_cpy,ap);
+                            current = sdscatvprintf(current,_format,_cpy);
+                            interpolated = 1;
+                            va_end(_cpy);
+
+                            /* Update current position (note: outer blocks
+                             * increment c twice so compensate here) */
+                            c = _p-1;
+                        }
+                    }
+
+                    /* Consume and discard vararg */
+                    va_arg(ap,void);
+                }
             }
             c++;
         }

test.c

@@ -71,6 +71,30 @@ static void test_format_commands() {
         len == 4+4+(3+2)+4+(1+2)+4+(1+2));
     free(cmd);
 
+    test("Format command with printf-delegation (long long): ");
+    len = redisFormatCommand(&cmd,"key:%08lld",1234ll);
+    test_cond(strncmp(cmd,"*1\r\n$12\r\nkey:00001234\r\n",len) == 0 &&
+        len == 4+5+(12+2));
+    free(cmd);
+
+    test("Format command with printf-delegation (float): ");
+    len = redisFormatCommand(&cmd,"v:%06.1f",12.34f);
+    test_cond(strncmp(cmd,"*1\r\n$8\r\nv:0012.3\r\n",len) == 0 &&
+        len == 4+4+(8+2));
+    free(cmd);
+
+    test("Format command with printf-delegation and extra interpolation: ");
+    len = redisFormatCommand(&cmd,"key:%d %b",1234,"foo",3);
+    test_cond(strncmp(cmd,"*2\r\n$8\r\nkey:1234\r\n$3\r\nfoo\r\n",len) == 0 &&
+        len == 4+4+(8+2)+4+(3+2));
+    free(cmd);
+
+    test("Format command with wrong printf format and extra interpolation: ");
+    len = redisFormatCommand(&cmd,"key:%08p %b",1234,"foo",3);
+    test_cond(strncmp(cmd,"*2\r\n$6\r\nkey:8p\r\n$3\r\nfoo\r\n",len) == 0 &&
+        len == 4+4+(6+2)+4+(3+2));
+    free(cmd);
+
     const char *argv[3];
     argv[0] = "SET";
     argv[1] = "foo\0xxx";